1. Field of the Invention
The present invention relates to a blower that transports gas.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2011-27079 discloses a micro-blower for dissipating heat generated inside a mobile electronic device or for supplying oxygen required to produce electric power in a fuel cell.
FIG. 12 is a cross-sectional view of a micro-blower 900 according to Japanese Unexamined Patent Application Publication No. 2011-27079. The micro-blower 900 includes an inner casing 2, an elastic metallic plate 5A, a piezoelectric element 5B, an outer casing 3 covering the outer side portion of the inner casing 2, and a lid member 9. The inner casing 2 is supported elastically on the outer casing 3 using a plurality of joining portions 4.
The inner casing 2 has a rectangular U-shaped cross section that is open in its lower portion. The inner casing 2 is joined to the elastic metallic plate 5A such that the opening is closed. Thus, the inner casing 2 and the elastic metallic plate 5A define a blower chamber 6. The inner casing 2 has an opening portion 8 enabling the inside and outside of the blower chamber 6 to communicate with each other. The piezoelectric element 5B is attached to a principal surface of the elastic metallic plate 5A opposite to the blower chamber 6.
The outer casing 3 has a discharge port 3A in a region that faces the opening portion 8. The outer casing 3 is provided with the lid member 9 for accommodating the inner casing 2. The lid member 9 has a suction port 9A in its central portion. The central axis passing through the center of the suction port 9A and extending along the thickness direction of the lid member 9 and the central axis passing through the center of the piezoelectric element 5B and extending along the thickness direction of the lid member 9 coincide with each other.
An influent channel 7 for air is formed between the outer casing 3 and the joined structure of the inner casing 2, elastic metallic plate 5A, and piezoelectric element 5B.
In the above-described configuration, when an alternating drive voltage is applied to the piezoelectric element 5B, the piezoelectric element 5B expands and contracts, and the expansion and contraction of the piezoelectric element 5B causes bending vibrations in the elastic metallic plate 5A. The bending distortion of the elastic metallic plate 5A causes the volume of the blower chamber 6 to periodically change.
In detail, when the alternating drive voltage is applied to the piezoelectric element 5B and the elastic metallic plate 5A is bent toward the piezoelectric element 5B, the volume of the blower chamber 6 increases. With this action, air outside the micro-blower 900 is sucked into the blower chamber 6 through the suction port 9A, influent channel 7, and opening portion 8. At this time, although there is no outflow of air from the blower chamber 6, inertial force of the air flow from the discharge port 3A to outside the micro-blower 900 is present.
Next, when the alternating drive voltage is applied to the piezoelectric element 5B and the elastic metallic plate 5A is bent toward the blower chamber 6, the volume of the blower chamber 6 decreases. With this action, the air inside the blower chamber 6 is discharged from the discharge port 3A through the opening portion 8 and influent channel 7.
At this time, the air flow discharged from the blower chamber 6 is discharged from the discharge port 3A while drawing the air outside the micro-blower 900 through the suction port 9A and the influent channel 7. Accordingly, the flow rate of air discharged from the discharge port 3A increases by the flow rate of the drawn air.
In the above-described manner, the discharge flow rate per power consumption in the micro-blower 900 increases.
However, the present inventor discovered that in the micro-blower 900 described in Japanese Unexamined Patent Application Publication No. 2011-27079, during the bending of the elastic metallic plate 5A toward the piezoelectric element 5B, an air flow BF leaking from the suction port 9A to outside the micro-blower 900 occurred.
That is, it was discovered that, because the flow rate of air drawn into the influent channel 7 is reduced by the flow rate of air leaking to outside the micro-blower 900 caused by the air flow BF, the discharge flow rate of air discharged from the discharge port 3A is reduced.
There has been a trend in recent years to reduce the power consumption in an electronic device equipped with the micro-blower having the above-described structure illustrated in FIG. 12. Thus, it is desired that the micro-blower have a high discharge flow rate with low power consumption.